Handcent questionSupport

I have installed handcent on my DI, and I agree that it is better than the stock app. However, if I receive a new message, it opens in the stock app, and not Handcent. I have to manually start handcent to use it. How do I get handcent to be my default app for texting? I have searched through the settings and can't find anything that makes it the default app. Thanks!